The overall objective of the research is to determine the nature of longterm interactions between marihuana and behavior. Towards this end, a more immediate goal is to investigate the effects of repeated administration of (minus) delta 9-trans-tetra-hydrocannabinol on the acquisition, performance and transfer of simple and complex behavior in rats and monkeys. The conceptual framework upon which the research is based assumes that the administration of marihuana constitutes an environmental change for the organism which produces overt changes in behavior. It is further assumed that behavior does not passively reflect marihuana action but rather adjusts dynamically over time to the presence of marihuana. One hypothesis derived from this conceptualization is that behavior will interact with marihuana to determine drug related phenomena such as marihuana tolerance and marihuana state-dependent learning. A portion of the proposed research is devoted to obtaining empirical verification for this hypothesis. The behavioral and drug administration methods proposed for the research are derived from conventional methods used in psychopharmacology and from the existing literature regarding the acute effects of marihuana.